Correct names in the ManifestList

[Fokko]

Looking at the manifest list, we see the following names:

  {
    "name" : "added_data_files_count",
    "type" : "int"
  }, {
    "name" : "existing_data_files_count",
    "type" : "int"
  }, {
    "name" : "deleted_data_files_count",
    "type" : "int"
  }

With the V2 spec the names have been changed:

This is just cosmetic, since the fields are looked up by ID, but would be nice to fix this to avoid any future confusion.

[s-akhtar-baig]

@Fokko, can you please assign this to me? Thanks!

[liurenjie1024]

@Fokko, can you please assign this to me? Thanks!

Done, thanks!

[gupteaj]

PR : #380